The present invention relates to pipes for carrying water and the like and, in particular, it concerns methods for connecting pipes and the corresponding pipe elements and connections.
Various techniques are known for connecting water pipes in fire prevention and domestic water supply systems. For many years, the only alternative to threading or flange connections was a labor intensive welding processes. More recently, a number of quick-assembly systems have been marketed. These systems seek to reduce the labor costs of assembly by providing various types of mechanical engagement to hold pipe ends together without requiring welding.
One quick-assembly system of particular interest is disclosed in U.S. Pat. No. 5,040,831 and is available commercially in the U.S. under the tradename POZ-LOK(copyright) from Southwestern Pipe, Inc. This system employs specially molded connector fittings which have slots on opposite sides. A pipe is inserted into the connector and a U-shaped bracket is hammered in through the slots. The bracket creates indents in the sides of the pipe, thereby retaining the pipe within the connector.
Another system is proposed by U.S. Pat. No. 5,779,283 to Kimura et al. This system is similar to the POZ-LOK(copyright) system, but uses a xe2x80x9ckeyxe2x80x9d member inserted in a channel formed in a connector on just one side of the pipe. The key member is disclosed as either a flat plate with a raised ridge or as a round pin. In the case of the round pin, the front of the pin is formed with a threaded section for fastening after insertion by use of a nut on the opposite side of the connector.
The POZ-LOK(copyright) and Kimura systems have at least two major advantages. Firstly, they are extremely quick and simple to assemble, requiring only a hammer to drive in the brackets. Secondly, the systems readily allows disassembly and subsequent reassembly without compromising the joint structure. However, the proposed systems are still far from ideal. In each case, precise alignment of the brackets during assembly is ensured by providing a heavy specially produced molded connector. The manufacturing cost of these connectors offsets to a large extent the cost advantages of labor savings. This is true even for iron piping. In the case of the increasingly popular copper piping, the manufacturing costs of such bulky connectors would be unacceptably high.
A further problem with practical implementation of systems such as that of Kimura et al. is to achieve reliable interconnection without risking damaging the inner pipe during insertion of the key member. Specifically, as best seen in FIG. 2 of the Kimura et al. reference, the depression formed in the inner pipe by the round pin of Kimura et al. is only a small proportion of the diameter of the pin. Although such a small indentation may be effective at low pressures, it risks unintended release in higher pressure applications. Furthermore, even if the threaded end of the pins were omitted, attempts to make a deeper indentation would be accompanied by risks of damaging the inner pipe due to shear forces in the direction of insertion of the pin. This is particularly true in thin-walled pipe applications.
In order to produce a quick-fit system with lower production costs, a number of systems use thin walled connectors which can readily be produced from modified sections of standard piping. An example of such a system is commercially available in the U.S. under the tradename PRESSFIT(trademark) from VICTAULIC(copyright).
The PRESSFIT(trademark) system employs a thin walled connector with an internal O-ring seal positioned around the end of a pipe. Engagement of the pipe within the connector is achieved using a special hydraulic circumferential press tool which makes a circumferential indent around the joint through both the connector and the pipe, thereby permanently fixing them together.
The PRESSFIT(trademark) system also suffers from a number of disadvantages. Firstly, assembly requires use of an expensive specialized tool which is also very heavy and awkward to handle. Furthermore, the jaws of the tool itself are specific to a given diameter of pipe such that considerable time and labor is required to switch the jaws each time a different gauge of pipe is encountered. Additionally, the joints produced are permanent and can only be dissembled by cutting out and replacing a section of pipe. This renders maintenance and service costs high.
There is therefore a need for a quick-fit method for connecting thin-walled pipes which does not require heavy molded fittings or specialized tools, and which can reliably be non-destructively assembled and subsequently dissembled for servicing. It would also be advantageous to provide pipe elements and connections corresponding to such methods.
The present invention is a method for connecting pipes in which mechanical engagement is achieved by insertion of a pin-like element.
According to the teachings of the present invention there is provided, a pipe joint assembly comprising: (a) a cylindrical pipe having an end with a given external pipe diameter; (b) a pipe element having a generally cylindrical terminal portion with an internal diameter no less than the given external pipe diameter for receiving the end, the terminal portion being formed with a substantially linear open ended channel extending in a direction substantially tangential to, but intersecting, the cylindrical pipe; and (c) a lock pin for insertion along the open ended channel so as to cause local inward deformation of the end, thereby locking the end and the pipe element together, wherein the lock pin has a parallel-sided shaft portion of minimum transverse dimension d and a tapered portion of length l tapering to a point, wherein l is no less than twice d and no greater than four times d.
According to a further feature of the present invention, the open ended channel is configured to allow insertion of the lock pin at an angle to a direction of extension of the open ended channel such that, on insertion of the lock pin within the channel, surfaces of the tapered portion bear simultaneously on surfaces of the end and of the open ended channel.
According to a further feature of the present invention, the open ended channel is configured such that, when the lock pin is inserted, the lock pin forms a depression of depth no less than half of d.
According to a further feature of the present invention, the lock pin is formed with l equal to about three times d.
According to a further feature of the present invention, the lock pin is formed with a pre-defined weakened region adjacent to a junction of the parallel-sided shaft portion and the tapered portion.
According to a further feature of the present invention, the lock pin has a substantially circular cross-section.
According to a further feature of the present invention, the minimum lateral dimension d is no snore than 20% of the given external pipe diameter.
According to a further feature of the present invention, the minimum lateral dimension d is between about 5% and about 15% of the given external pipe diameter.
According to a further feature of the present invention, the terminal portion has a wall of thickness no more than about 10% of the given external pipe diameter.
According to a further feature of the present invention, the terminal portion features an annular recess formed around an internal surface of the terminal portion.
According to a further feature of the present invention, the terminal portion has a connector end, the open ended channel being located between the connector end and the annular recess.
According to a further feature of the present invention, there is also provided a sealing element located within the annular recess.
According to a further feature of the present invention, the pipe element is an angled connector.
According to a further feature of the present invention, the pipe element is a three-way connector.
There is also provided according to the teachings of the present invention, a method for interlocking an end of a cylindrical pipe of given external diameter within a connector formed with an internal bore for receiving the pipe end and an open-ended channel extending in a direction substantially tangential to the internal bore by use of a lock pin having a tapered end portion and a length, the method comprising the steps of: (a) inserting the end of the pipe within the internal bore so that a surface of the open-ended channel and a surface of the pipe end together form a wedge-shaped crevice; (b) positioning the lock pin with its tapered end portion lodged within the wedge-shaped crevice so that the length of the lock pin is non-parallel to the extensional direction of the open-ended channel; and (c) applying force to the lock pin so as to advance the lock pin through a combined linear and rotational displacement so as to cause local inward deformation of the pipe end until the lock pin reaches a locking position in which the length of the lock pin lies parallel to the extensional direction of the open-ended channel, thereby locking the pipe end within the connector.
According to a further feature of the present invention, the lock pin forms a depression in the pipe end to a depth of at least half a thickness of the lock pin.
According to a further feature of the present invention, the tapered end of the lock pin is detached after the lock pin has reached the locking position.